It has been a while since I’ve presented the GISS, UK Met Office and NCDC global land surface air temperature plus sea surface temperature products. I’ve decided to add them to the datasets I update monthly.
I’ll present each of the datasets individually, starting in January 1979, using the suppliers’ standard base years for anomalies. 1979 is the start year of the lower troposphere temperature products (not included), so it’s a logical start time for these short-term data presentations. The GISS, UK Met Office and NCDC products with linear trends are then presented in a comparison graph, using the base years of 1981-2010. And for those wanting a better look at the most recent wiggles, the last comparison graph starts in January 2003—the last decade plus. The final graph is the average of the 3 products.
GISS LAND OCEAN TEMPERATURE INDEX (LOTI)
Introduction: The GISS Land Ocean Temperature Index (LOTI) data is a product of the Goddard Institute for Space Studies. Starting with their January 2013 update, it uses NCDC ERSST.v3b sea surface temperature data. The impact of the recent change in sea surface temperature datasets is discussed here. GISS adjusts GHCN and other land surface temperature data via a number of methods and infills missing data using 1200km smoothing. Refer to the GISS description here. Unlike the UK Met Office and NCDC products, GISS masks sea surface temperature data at the poles where seasonal sea ice exists, and they extend land surface temperature data out over the oceans in those locations. Refer to the discussions here and here. GISS uses the base years of 1951-1980 as the reference period for anomalies. The data source is here.
Update: The February 2013 GISS global temperature anomaly is 0.49 deg C. It dropped -0.11 deg C since January 2013.
UK MET OFFICE HADCRUT4
Introduction: The UK Met Office HADCRUT4 dataset merges CRUTEM4 land-surface air temperature dataset and the HadSST3 sea-surface temperature (SST) dataset. CRUTEM4 is the product of the combined efforts of the Met Office Hadley Centre and the Climatic Research Unit at the University of East Anglia. And HadSST3 is a product of the Hadley Centre. Unlike the GISS and NCDC products, missing data is not infilled in the HADCRUT4 product. That is, if a 5-deg latitude by 5-deg longitude grid does not have a temperature anomaly value in a given month, it is not included in the global average value of HADCRUT4. The HADCRUT4 dataset is described in the Morice et al (2012) paper here. The CRUTEM4 data is described in Jones et al (2012) here. And the HadSST3 data is presented in the 2-part Kennedy et al (2012) paper here and here. The UKMO uses the base years of 1961-1990 for anomalies. The data source is here.
Update: The February 2013 HADCRUT4 global temperature anomaly is +0.48 deg C. It increased +0.05 deg C since January 2013.
NCDC GLOBAL SURFACE TEMPERATURE ANOMALIES
Introduction: The NOAA Global (Land and Ocean) Surface Temperature Anomaly dataset is a product of the National Climatic Data Center (NCDC). NCDC merges their Extended Reconstructed Sea Surface Temperature version 3b (ERSST.v3b) with the Global Historical Climatology Network-Monthly (GHCN-M) version 3.2.0 data for land surface air temperature anomalies. NOAA infills missing data for both land and sea surface temperature datasets using methods presented in Smith et al (2008). The data source is here. NCDC uses 1901 to 2000 for the base years for anomalies.
Update: The February 2013 NCDC global land plus sea surface temperature anomaly is +0.58 deg C. It increased +0.04 deg C since January 2013.
The three datasets are compared in the next two time-series graphs. The first graph compares the GISS, HADCRUT4 and NCDC global surface temperature anomaly products starting in 1979. It also includes the linear trends. Because the three datasets share common source data, (GISS and NCDC also use the same sea surface temperature data) it should come as no surprise that they are so similar. For those wanting a closer look at the more recent wiggles, the second graph starts in 2003. Both of the comparisons present the anomalies using the base years of 1981 to 2010. Referring to their discussion under FAQ 9 here, according to NOAA:
This period is used in order to comply with a recommended World Meteorological Organization (WMO) Policy, which suggests using the latest decade for the 30-year average.
Comparison Starting in 1979
Comparison Starting in 2003
The last graph presents the average of the GISS, HADCRUT and NCDC land plus sea surface temperature anomaly products. The flatness of the data since 2001 is very obvious, as is the fact that surface temperatures have rarely risen above those created by the 1997/98 El Niño.
Average of Global Land+Sea Surface Temperature Anomaly Products